FIGS. 14-16 illustrate a conventional precast floor panel 210 for use as all or part of a building floor. The precast floor panel 210 includes a monolithic concrete slab 212 that is poured and cured in a mold 214. The mold 214 is formed from flat sheets of expanded polystyrene foam that will remain attached to the cured concrete, and from mold parts that define exposed outer surfaces that will be removed from the concrete after curing. The mold parts removed after curing may be made of plywood, timber, foam sheets, or other suitable material.
The foam sheets that remain attached to the concrete provide insulation (thermal resistance) and reduce noise transmittal in the finished floor panel 210. A number of floor panels 210 can be connected side-by-side and/or end-to-end in a conventional manner for constructing a larger building floor.
The concrete slab 212 is generally rectangular-shaped and includes a reinforced top sheet or deck 224 that defines a flat floor extending the width and length of the floor panel 210. A number of parallel, spaced apart stems 226 are also formed integral with the deck 224 on the bottom side of the deck 224. The stems 226 extend along the length of the floor panel 210 and connect together a pair of end blocks 228, 230.
The end blocks 228, 230 on the bottom of the deck 224 are adjacent the ends of the deck 224 and extend the width of the floor panel 210. The blocks 228, 230 each extend about the same height as the total height of a stem 226 plus the thickness of the foam sheet on the bottom of the stem, and are each typically between two inches and three inches wide.
The blocks 228, 230 resist longitudinal cracking of the deck. The blocks 228, 230 allow floor panels 210 to be set between wall members to allow stacking of floor panels 210 for multi-story construction and can act as beams to span gaps if the wall members cannot provide continuous support of the blocks. The blocks 228, 230 also allow stacking of floor panels 210 during storage and transport.
The illustrated deck 224 typically has a thickness of between one inch and one-and-one-quarter inches, and a length of between eight feet and fifty feet. The concrete forming the deck 224 can be reinforced with reinforcement bars, reinforcement wires, wire mesh, fibers, or the like embedded in the soft concrete or mixed into the concrete prior to pouring as is known in the concrete construction art. An optional light-weight, non-structural leveling coat can be applied to the top of the deck 224.
The stems 226 extend away from the bottom deck surface 234 and extend the span of the slab 212 between the end blocks 228, 230. The illustrated stems 226 are spaced apart from one another on two-foot centers, each stem 226 having a generally rectangular cross-section as viewed in FIG. 11 with a preferred width of between two inches and fifteen inches. The stems 226 extend from the surface 234 a preferred distance of between six inches and sixteen inches.
A stem 226 is pre-stressed by strands 240, 242 extending the length of the stem 226. In shorter stems, reinforcing bars or rods can be used instead for pre-stressing or reinforcing the stems.
The insulation mold 214 is constructed from flat foam sheets that are trimmed to the required length and width and assembled together to form the mold. The flat sides of the sheets automatically form smooth surfaces that define the facing smooth surfaces of the floor panel 210. The thickness of the sheet essentially defines the thickness of the insulation insulating the slab at the sheet's location in the mold 214.
The mold 214 includes generally U-shaped mold cavities that define the stems 226 and flat decking sheets 244 between the mold cavities that define the bottom of the deck. Each mold cavity is made of two sheet segments 246 that form the leg of the “U” and a sheet segment joining the legs 246. The decking sheets 244 are trimmed to the appropriate length and width from two-inch thick foam sheets. The “U” sheet segments are each trimmed to the appropriate length and width from one-and-one-eighth-inch thick foam sheets.
Joints join the decking sheets 244 and the leg sheets 246 to form the mold transitions from the stems to the deck. In the illustrated embodiment the joints are rabbet joints, with the leg sheets 246 received in rabbet grooves in the decking sheets 244. The joints define generally planar seams between facing surfaces of the sheets 244, 246 that extend along the length of the stems.
A metal or wood wall stud 248 is attached to the bottom side of each “U” mold segment which can be used for attachment of drywall or other finishing materials to the finished floor. The stud 248 can be provided with protrusions that extend into the mold cavity of the mold 214 that enable the stud 248 to be rigidly held in the set concrete forming the stem 226. A tube or shaft can be placed in the stem portion of the mold 214 to form an optional through-passage 250 (shown in phantom in FIG. 10) for passing wires, cabling, bolts, or the like through the stem 226. Wire mesh or the like (not shown) may also be placed in each stem mold portion prior to the concrete pour, the mesh extending the full or partial length of the stem 226 to resist shear forces.
Precast floor panels 210 have proven to be cost effective and are well-received as an alternative to cast-in-place concrete floors. Nevertheless, there is room for improvement. Furthermore, a truck can only deliver a limited number of floor panels 210 to a job site due to the size and weight of the floor panels 210.